ZOOLOGY AND BOTANT, MICROSCOPY, ETC. 727 



apposition with their tme legs ; this leech-like mode of progression is 

 less satisfactory, but its defects are made up for by the protective 

 colouring of the bodies of these caterpillars. 



Colour-relation between Pupae and Surroundings.* — Mr. W. White 

 describes some experiments made by Mr. G. C. Griffiths upon the colour- 

 relation between the pupas of Pieris rapse and their immediate sur- 

 roundings. 



(a) Poulton's observation that dark surroundings exercise a retarding 

 influence upon the period before pupation is confirmed. (h) To all 

 appearance the freshly formed pupa is not photographically sensitive. 

 (c) The general results of the colours themselves also entirely confirm 

 Poulton's observations, notably in the case of dark pupae produced by 

 black and of green pupae produced by yellow, (d) The special eff'ects 

 of yellow surroundings in arresting the formation of dark superficial 

 pigment, and in tending towards the production of green pupae, were 

 very striking, and confirm Poulton's suggestion that rays from this part 

 of the spectrum, when predominant in the light incident upon the sus- 

 ceptible larva, determine the production of these results whenever green 

 pupae are produced by the influence of surroundings. When green pupfe 

 of Pieris are produced, as in nature, on green leaves, it is probable that 

 the effect is wholly due to the reflected yellow rays. Though these 

 experiments do not exactly ftirnish materials for new conclusions, they 

 are valuable as independent corroborations of Poulton's results. 



Aphides. t — Dr. H. F. Kessler discusses the development and life- 

 history of Cfhaitophorus aceris Koch, Ch. testudinatus Thornton, Cli. lijro- 

 picfus Kessler, which he regards as three distinct species instead of as 

 one (^Aphis aceris Linne) as they have been hitherto considered. 



B. Myriopoda. 



Post-embryonic Development of Julus terrestris.i — In his second 

 memoir on the development of the Myriopoda, Mr. F. G. Heathcote 

 describes the development of different organs. The mode of develop- 

 ment of the somites is essentially the same as that of Peripatus, for the 

 ccelomic spaces are found to have nothing to do with the body-cavity or 

 vascular system of Julus ; the body-cavity is a series of spaces contained 

 between the gut and the body-wall, and is a pseudocoele. With this 

 general resemblance there are considerable differences in the details. 

 In the hinder part of the body of Julus, that is behind the third body- 

 segment, part of the somite is in the limbs, and part in the body ; the 

 latter passes towards the top of the nerve-cord, and not to the dorsal part 

 of the body as in Peripatus ; the part of the somite within the limbs, 

 which in Peripatus forms the nephridium and its vesicle, furnishes in 

 Julus the muscles of the limbs. 



One of the most interesting points about the development of the 

 somites is the fact that the so-called double segments have two meso- 

 blastic segments each ; this is against the suggestion of Balfour that the 

 double segments might represent single segments which had developed 

 a second pair of limbs, and had altered the nervous system and other 

 organs to suit them. 



* Trans. Entomol. Soc. Lond., ii. (1888) pp. 247-67. 



t Nova Acta Acad. Caes. Leop.-Carol., 11. (1887) pp. 151-79 (1 pi.). 



X Phil. Trans., clxxix. B (1888) pp. 157-79 (4 pis.). 



3 D 2 



